244 
POISONS ! THEIR EFFECTS AND DETECTION. 
[§ 302. 
§302. The Detection of Phosphorus.— The following are the chief 
methods in use for the separation and detection of phosphorus :_ 1 
1. Mitscherlich’s Process.— The essential feature of this process is 
simply distillation of free phosphorus, and observation of its luminous 
properties as the vapour condenses in the condensing tube. The condi¬ 
tions necessary for success are : (1) that the apparatus should be in total 
darkness ; 2 and (2) that there should be no substance present, such 
as alcohol or ammonia, 3 which, distilling over with the phosphorus 
vapour, could destroy its luminosity. A convenient apparatus, and one 
certain to be in all laboratories, is an ordinary Florence flask, containing 
the liquid to be tested, fitted to a glass Liebig’s condenser, supported on 
an iron sand-bath (which may, or may not, have a thin layer of sand), and 
heated by a Fletcher’s low-temperature burner. The distillate is received 
into a flask. This apparatus, if in darkness, works well; but should the 
observer wish to work in daylight, the condenser must be enclosed in 
a box perfectly impervious to light, and having a hole through which 
the luminosity of the tube may be seen, the head of the operator and the 
box being covered with a cloth. If there be a stream of water passing 
continuously through the condenser, a beautiful luminous ring of light 
appears in the upper part of the tube, where it remains fixed for some 
time. Should, however, the refrigeration be imperfect, the luminosity 
travels slowly down the tube into the receiver. In any case, the deli¬ 
cacy of the test is extraordinary. 4 If the organic liquid is alkaline, or 
even neutral, there will certainly be some evolution of ammonia, which 
will distil over before the phosphorus, and retard (or, if in sufficient 
quantity, destroy) the luminosity. In such a case it is well, -as a precau¬ 
tion, to add enough sulphuric acid to fix the ammonia, omitting such 
addition if the liquid to be operated upon is acid. 
2. The Production of Phosphine (PH 3 ).—Any method which pro¬ 
duces phosphine (phosphuretted hydrogen), enabling that gas to be 
passed through nitrate of silver solution, may be used for the detection 
of phosphorus. Thus, Sonnenschein states that he has found phos- 
It has been recommended to dissolve the phosphorus out from organic matters 
by carbon disulphide. On evaporation of the latter the phosphorus is recognised 
by its physical properties. Such a method is of but limited application, although 
1 may sometimes be found useful. The senior author has successfully employed it 
in the extraction of phosphorus from the crop of a fowl; but on this occasion it 
iiappened to be present in large quantity. 
2 Any considerable amount of phosphorescence can, however, be observed in 
twilight. 
3 Many volatile substances destroy the luminous appearance of phosphorus 
vapour, e.g chlonne, hydric sulphide, sulphur dioxide, carbon disulphide, ether, 
alcohol, petroleum, turpentine, creasote, and most essential oils. On the other hand’ 
romme, hydrochloric acid, camphor, and carbonate of ammonia do not seem to inter¬ 
fere much with the phosphorescence. 
4 ^fnius states that he and Neubauer, with 1 mgrm. of phosphorus in 200,000 
recognised the light, which lasted for half an hour.— Zeitschr. f. anal. Chem., i. 336. 
